From the Editor
January, 2014. Throughout the last decade, teams of experts reviewed the diagnostic classification system of the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association (APA), to determine what evidence-based revisions should be recommended for DSM-5. Now published, DSM-5 incorporates the final approved revisions, following an interactive public and scientific dialogue, as sequential drafts of proposed changes were posted online for review and comment. Early in the process, scientific conferences were jointly sponsored by the APA and the National Institute of Mental Health (NIMH), the proceedings of which were published in a series of monographs referred to as “A Research Agenda for DSM-V.” In 2002, in one of the “white papers” in the initial monograph of this series, Rounsaville et al. contended that “well-informed clinicians and researchers have suggested that variation in psychiatric symptomatology may better be represented by dimensions than by a set of categories….”1 Looking back over many years, in a monograph entitled “The Conceptual Evolution of DSM-5,” Regier et al. noted the growing recognition of the predominance of mixed clinical syndromes, the lack of “points of rarity” between disorders (yet presumably a fundamental feature of a categorical system such as the DSM), and the dimensional nature of complex polygenic psychiatric disorders interacting with epigenetic gene-activating experiences across a broad spectrum.2 Steven Hyman, former Director of NIMH and a key consultant for DSM-5, argued that disorders “in which evidence favors a dimensional approach include major depression…, obsessive-compulsive disorder…, autism…, attention deficit hyperactivity disorder…, and personality disorders,” adding that for all of these diagnoses, “symptoms listed in their criterion sets are also normally distributed in the general population.”3
In this issue of the Journal, Saxbe and Barkley present a most interesting review of a particular aspect of attention-deficit/hyperactivity disorder (ADHD), one that clearly illustrates the dimensional/categorical challenge. In the broad realm of autism spectrum disorder and ADHD, they call our attention to a condition referred to as “sluggish cognitive tempo” (SCT) that was not incorporated in DSM-5 but that, they and others contend, would identify a group of patients distinctly different from those with ADHD itself, though some characteristics or criteria could be shared. The term has been proposed to recognize patients with attention deficit symptoms but without hyperactivity. Saxbe and Barkley do not endorse the proposed term “sluggish cognitive tempo” (and I agree with them), preferring something like “concentration deficit disorder” or variants thereof. More important than the label, however, is the need for more research to confirm the validity of SCT and to explore whether specific treatment options might be indicated for this condition.
So, dimensional or categorical? This debate is, of course, center stage in the realm of personality disorders, as any review of that aspect of DSM-5 would reveal. But controversy and debate about which approach serves us best when attempting to identify the essential nature of a specific psychiatric disorder (e.g., to meet the Robbins and Guze4 criteria to define an illness) surround many if not most conditions in the diagnostic manual. In my opinion, DSM-5 and its predecessors represent not only the most recent scientific findings about psychopathology, but also a language of communication, to enable patients, families, clinicians, and researchers to approach a clear-headed understanding of the nature of different types of suffering and to select the right road to relief. Diagnostic labels are handles, tools, approximations, conventions, attempts at a common language. They do not represent fixed, separate, unrelated entities, but they are necessary and they help us do our job. Nonetheless, I believe that the dimensional/categorical debate is here to stay!
1. Rounsaville BJ, Alarcon RD, Andrews G, et al.Kupfer DJ, First MB, Regier DA.Basic nomenclature issues for DSM-V.A research agenda for DSM-V.2002.Washington, DC:American Psychiatric Association.
2. Regier DA, Narrow WE, Kuhl EA, et al.Regier DA, Narrow WE, Kuhl EA, et al..Introduction.The conceptual evolution of DSM-5.2011.Arlington, VA:American Psychiatric Publishing.
3. Hyman SE.The diagnosis of mental disorders: The problem of reification.Ann Rev Clin Psychol.2010;6:155–79.
4. Robins E, Guze SB.Establishment of diagnostic validity in psychiatric illness: Its application to schizophrenia.Am J Psychiatry.1970;126:983–6.